Transparent conductive film, low-reflectivity transparent conductive film, and display device

ABSTRACT

A transparent conductive film having a transparent conductive layer containing at least two types of metals wherein the film is high in transparency, tonability, and conductivity, and provides for static prevention and electromagnetic shielding effects, enables adjustment of the tone of transmitted images, and has durability with respect to saline resistance, acid resistance, oxidation resistance, and ultraviolet resistance.

TECHNICAL FIELD

The present invention relates to a transparent conductive film havinghigh transparency, tonability, and conductivity, exceptional anti-staticeffects and electromagnetic shielding effects, and greatly improveddurability such as with respect to saline resistance, acid resistance,oxidation resistance, and ultraviolet resistance; a low-reflectivitytransparent conductive film having exceptional anti-reflective effectsin addition to the above-mentioned properties; and anelectromagnetically shielded display device having this low-reflectivitytransparent conductive film formed on the display screen.

BACKGROUND ART

Conventionally, transparent materials having high dielectric constantssuch as glasses and plastics tend to accumulate static electricity andallow transmission of electromagnetic waves. In particular, in cathoderay tubes and plasma displays which are often used for TV Braun tubesand computer displays, dust can collect due to static electricitygenerated on the display screen so as to lower the visibility, andelectromagnetic waves can be radiated to affect the environs. For thisreason, transparent conductive films have been affixed to the displayscreens of cathode ray tubes and plasma displays used in TV Braun tubesand computer displays for the purposes of preventing static electricityand/or shielding electromagnetic waves.

Conventional transparent conductive films are produced by forming atransparent conductive oxide such as indium oxide on a display screen bymeans of sputtering or vapor deposition and affixing this to the displayscreen of a display device, or by coating the front surface of a displayscreen with a dispersion fluid of antimony-doped tin oxide and a silicasol binder. Additionally, there are transparent conductive films whichare provided with a reflection preventing function by making use ofinterference effects which occur due to reflection at a plurality ofthin film surfaces, by laminating the top layer and/or the bottom layerof the transparent conductive film with at least one transparentanti-reflective layer having a refractive index different from thetransparent conductive layer.

As conventional methods for forming a transparent conductive film whichnot only prevents the accumulation of static electricity but also hasconductivity high enough to shield electromagnetic radiation on thedisplay screen of a display device, a process of putting the displayscreen into a vapor deposition oven and depositing indium oxidecompounds or tin oxide compounds thereon (PVD process), and a process offorming a transparent conductive film on the display screen by thermaldecomposition of organic compounds such as indium or tin, or salinesolution (CVD process) are known.

While the transparent conductive films formed by the above-mentionedmethods are sufficiently transparent when used only as anti-static filmsin which case the film thickness can be small, when used aselectromagnet wave shielding layers or electrode films, they must bemade somewhat thicker because they require high conductivity, as aresult of which the transparency can be reduced, and the screendarkened, as well as giving rise to problems such as absorption ofspecific optical wavelengths which can cause coloring of the conductivefilm and cause unnatural changes in the hue of the transmitted images.Additionally, since a vacuum or high temperatures are required in orderto form a film using the above-mentioned PVD process or CVD process, thecost of investments in order to form a transparent conductive film on alarge-area substrate can become extremely high, the efficiency can bedegraded, and the production costs can inflate.

Coating processes have been proposed for efficiently forming transparentconductive films on large substrates while suppressing equipmentinvestments. For example, coating materials containing organic indiumcompounds is disclosed in Japanese Patent Application, First PublicationNo. Sho 52-1497, and coating materials having indium salts or tin saltsdissolved in water or organic solvents are disclosed in Japanese PatentApplication, First Publication No. Sho 63-6401, Japanese PatentApplication, First Publication No. Sho 55-51737, Japanese PatentApplication, First Publication No. Sho 58-82407, Japanese PatentApplication, First Publication No. Sho 57-36714, and Japanese PatentApplication, First Publication No. Sho 60-22507. However, since theformation of transparent conductive films using these coating materialsrequires heat treatment at high temperatures of at least 350° C. aftercoating the substrate, there are limitations to the materials which canbe used for the substrate, and there are many restrictions with regardto the production steps.

Coating materials wherein microparticles or colloids of transparentconductive oxides such as tin oxide and indium oxide are dispersed inpolymer solutions or binder resins are disclosed in Japanese PatentApplication, Second Publication No. Sho 35-6616, Japanese PatentApplication, First Publication No. Sho 57-85866, Japanese PatentApplication, First Publication No. Sho 58-91777, and Japanese PatentApplication, First Publication No. Sho 62-278705. These coatingmaterials are held to be capable of forming transparent conductive filmsat relatively low temperatures.

However, all of the above-mentioned transparent conductive films requirethe thickness of the coating film to be made small in order to obtain apractical level of transparency; making them thin causes theconductivity to be reduced, so that although they are useful for thepurposes of static prevention, they are insufficient for the purposes ofelectrical shielding; making them thick causes the transparency to bereduced, which darkens the screen and limits the possibilities of use.

As a transparent conductive film having exceptional electromagneticshielding effects and anti-reflection effects, Japanese PatentApplication, First Publication No. Hei 8-77832 disclosed one comprisinga transparent conductive layer composed of metallic microparticleshaving an average grain size of 2-20 nm and a transparent coat having alower refractive index. Although electromagnetic shielding effects canbe expected of this transparent conductive film, it fails to provide asolution to the problem of absorption occurring at specific wavelengthsof transmitted light depending on the light transmission spectrum of themetal, thereby coloring the conductive film and unnaturally changing thehue of the transmitted image, and it also cannot be expected to providesufficient anti-reflective effects.

Aside from the above, if the purpose is simply to form a conductivefilm, Japanese Patent Application, First Publication No. Hei 4-23484discloses a process of coating with a coating material wherein reducedmetallic colloid particles are dispersed in a photosensitive resin, andJapanese Patent Application, First Publication No. Hei 4-196009discloses a process of printing a conductive paste onto a dielectricgreen sheet using a screen printing method, but these are bothnon-transparent and do not result in a transparent conductive film.

The present invention has been made to resolve the above problems, andtherefore its object is to offer a transparent conductive film havinghigh transparency, tonability, and conductivity, exceptional anti-staticeffects and electromagnetic shielding effects, adjusted tone of thetransmitted images, and greatly improved durability such as with respectto saline resistance, acid resistance, oxidation resistance, andultraviolet resistance; a low-reflectivity transparent conductive filmhaving exceptional anti-reflective effects in addition to theabove-mentioned properties; and an electromagnetically shielded displaydevice having this low-reflectivity transparent conductive film formedon the display screen.

DISCLOSURE OF THE INVENTION

The present inventors achieved the present invention as a result ofdiligent research for resolving the above-mentioned problems bydiscovering that a transparent conductive film having a transparentconductive layer containing at least two types of metals in an amount ofat least 10% by weight is capable of being produced at a relatively lowcost, has high transparency, tonability, and conductivity, exceptionalanti-static effects and electromagnetic shielding effects, enablesadjustment of the tone of the transmitted images and has greatlyimproved durability such as with respect to saline resistance, acidresistance, oxidation resistance, and ultraviolet resistance.

Thus, the present invention offers a transparent conductive film,comprising a transparent conductive layer containing at least two typesof metals in a total amount of at least 10% by weight.

In the above, the at least two types of metal sin the transparentconductive layer should preferably be selected from the group consistingof silver, gold, copper, platinum, palladium, ruthenium, rhodium,iridium, osmium, rhenium, and nickel.

In the above, one of the at least two types of metals in the transparentconductive layer should preferably be silver.

In the above, one of the at least two type of metals in the transparentconductive layer should preferably be palladium.

In the above, the transparent conductive layer should preferably containpalladium and silver, in a ratio Pd:Ag within the range of 30-99% byweight:70-1% by weight.

In the above, at least a portion of the metals in the transparentconductive layer should preferably be fused to form a continuousmetallic thin film.

In the above, at least a portion of the at least two types of metals inthe transparent conductive layer should preferably form an alloy.

In the above, the transparent conductive layer should preferably beformed by applying to a base material atransparent-conductive-film-forming coating material containing at leasttwo types of metallic microparticles having an average grain size of 100nm or less, then baking at a temperature within the range of 130-250° C.This transparent-conductive-film-forming coating material shouldpreferably contain alcohol in an amount of at least 45% by weight.

The present invention also offers a low-reflectivity transparentconductive film comprising a transparent conductive film as describedabove, and at least one transparent thin film provided above and/orbelow the transparent conductive film, having a refractive indexdifferent from the refractive index of the transparent conductive layer.

In the above, the transparent thin film should preferably contain SiO₂.

In the above, a transparent rough layer should preferably be formed asan outermost layer of the low-reflectivity transparent conductive film.

In the above, at least one layer constituting the low-reflectivitytransparent conductive film should preferably contain a colorant.

The present invention also offers a display device having alow-reflectivity transparent conductive film in accordance with any oneof claims 10-13 formed on a display screen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view showing a preferred low-reflectivitytransparent conductive film and display device according to the presentinvention;

FIG. 2 is an X-ray diffraction diagram for a preferred embodiment of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An example of the best mode for carrying out the present invention shallbe explained with reference to the attached FIG. 1. In FIG. 1, thislow-reflectivity transparent conductive film 10 is formed on the frontsurface of the display screen 3 of a display device and is formed bysequentially laminating a transparent conductive film 1 and atransparent thin film 2 having a refractive index different from thistransparent conductive film 1 onto the display screen 3.

This transparent conductive layer 1 contains palladium and silver in atotal amount of at least 10% by weight. The proportions of palladium andsilver in the mixture, expressed as a ratio of Pd:Ag, should preferablybe within the range of 30-99% by weight:70-1% by weight. Although thepalladium and silver may be contained in the transparent conductivelayer 1 as respectively independent microparticles, at least a portionof them should preferably be fused to form a metallic thin film which iscontinuous, and at least one portion thereof forms an alloy composed ofpalladium and silver.

When palladium and silver are present in the form of microparticles inthis transparent conductive layer 1, the microparticles are in mutualcontact, and at least a portion thereof is fused to form a continuousalloy thin film. Therefore, not only is the conductivity high as aresult of which the static prevention effects and electromagneticshielding effects are exceptional, but the transparency is also high,and since a portion of the metal is palladium, the conductivity is notlost even in a metal-corroding environment such as in saline water orsunlight, and exceptional durability is obtained such as with respect tosaline resistance, acid resistance, oxidation resistance, andultraviolet resistance. Additionally, since a portion of the metal issilver, sufficient conductivity can be ensured while enabling productionat a reduced cost in comparison to use of only palladium.

This transparent conductive layer 1 contains palladium microparticlesand silver microparticles having an average grain size of preferably 20nm or less, and is preferably formed by coating the display screen 3with a coating containing at least 45% by weight of alcohol by using aspin coater, then baking at a temperature of preferably 150-250° C. Thepresent inventors discovered that since the average grain sizes of themetallic microparticles contained in this coating are 20 nm or less, themicroparticles will fuse even if the baking temperature is as low as150-250° C., so that an alloy thin film is at least partially formed.Additionally, the alcohol in this coating lowers the viscosity andsurface tension of coatings containing metallic microparticles, therebyforming a coating film having a uniform thickness, and is alsoparticularly effective in preventing the metallic microparticles fromforming secondary particles.

The preferred low-reflectivity transparent conductive film 10 of thepresent invention shown in FIG. 1 has a single layer of a transparentthin film 2 having a refractive index different from the refractiveindex of the transparent conductive layer 1 formed on top of thetransparent conductive layer 1. This transparent thin film 2 is formedfrom SiO₂ or the like which has a relative low refractive index. Thepresence of this transparent thin film 2 above the transparentconductive layer 1 effectively prevents reflection of ambient light fromthe low-reflectivity transparent conductive film 10, and contributesreflection prevention in addition to the above-mentioned transparency,static prevention, electromagnetic shielding, and durability.

In a more preferable low-reflectivity transparent conductive filmaccording to the present invention, a transparent rough layer is formedas the outermost layer. This transparent rough layer is preferablycomposed of a transparent film having a low refractive index, and has asurface with a rough profile so as to scatter light reflected from thesurface of the low-reflectivity transparent conductive film and give thedisplay screen an anti-glare effect.

In a more preferable low-reflectivity transparent conductive filmaccording to the present invention, at least one of the transparentconductive layer 1 or the transparent thin film 2 contains a colorant.This colorant absorbs light in a specific wavelength band within therange of 400-800 nm which is the wavelength band of visible lightaccording to the type of metal contained in the transparent conductivelayer, and is added for the purposes of improving the contrast of thetransmitted images and/or for the purposes of adjusting the hue when thetransmitted images appear to have an unnatural color, as a result ofwhich it is possible to obtain a low-reflectivity transparent conductivefilm with improved perceptibility.

The preferred display device of the present invention has theabove-described low-reflectivity transparent conductive film 10 formedon the front surface of the display screen 3 as shown in FIG. 1, due towhich the display device of the present invention is such that staticelectricity is prevented so as to prevent the accumulation of dust orthe like, electromagnetic waves are effectively shielded to preventedvarious types of electromagnetic disturbances, the screen has hightransparency so that the transmitted images are bright, the reflectionof ambient light is effectively prevented so that the perceptibility ishigh, and the transmitted images are clear, and the hue is adjusted sothat the transmitted images have colors which appear natural.Furthermore, degradation of the properties is prevented over longperiods of time under severe environmental conditions.

Next, each component of the present invention shall be explained indetail.

The transparent conductive film of the present invention essentially hasa transparent conductive layer containing at least two types of metalsin a total of at least 10% by weight.

Examples of metals which can be suitably used for the above are thosehaving good conductivity and relatively low susceptibility to corrosion,for example, silver, gold, cooper, platinum, palladium, ruthenium,rhodium, iridium, osmium, rhenium, and nickel. While at least two typesof these metals can be combined arbitrarily, those having hightransparency and low absorption at specific wavelengths so as to givethe transmitted images a natural hue, and with good conductivity shouldpreferably be selected.

In the above-mentioned transparent conductive film, at least one of thetwo types of metals should preferably be silver. The reason for this isthat silver can be obtained relatively easily and economically in theform of a colloidal dispersion fluid, has high conductivity andexceptional static prevention and electromagnetic shielding effects, andforms a highly transparent conductive layer.

Palladium should preferably be used as a metal in combination withsilver. The reason for this is that palladium has high conductivity andis chemically stable, is highly resistant to chloride, sulfide, andoxide atmospheres, and will not change the hue of transmitted lightbecause it has no absorption in specific wavelength bands in the rangeof 400-800 nm which is the wavelength band of visible light, so as notto degrade the visibility of transmitted images.

While silver is a metal having relatively low durability with respect tosaline resistance, acid resistance, and the like, using silver incombination with palladium allows for the formation of a transparentconductive film with exceptional durability with respect to salineresistance, acid resistance, and the like because palladium and silversill fuse to form a Pd--Ag alloy even at relatively low bakingtemperatures of 150-250° C. when the transparent conductive layer isformed.

When palladium and silver are used together, the proportional contentshould preferably be such that the ratio Pd:Ag is within the range of30-99% by weight:70-1% by weight. If the proportional content ofpalladium is higher, the durability of the transparent conductive filmwith respect to saline resistance, acid resistance, and the like willincrease.

When silver is used in at least a portion of the metals in thetransparent conductive layer, gold is another example of a metal whichmay be used therewith. While silver has a characteristic absorption inthe shorter wavelengths of the visible light range and as a result has atendency to apply a rather yellowish color to the transmitted images,blending in a relatively small amount of gold causes the transmittedspectrum to become flattened in the visible light range, therebycorrecting the deviation in the hue of the transmitted images.

The reason the content of the metals in the transparent conductive layeris made at least 10% by weight is that the conductivity is reduced ifthe content is less than 10% by weight, and it becomes difficult toobtain a substantial electromagnetic shielding effect.

The metals in the transparent conductive layer may be present in theform of respectively independent microparticles, may be fused in atleast one portion to form a continuous metallic thin film, may have atleast two types of metals fused in at least one portion to form an alloyso as to result in an alloy thin film, or may have microparticles and analloy thin film in a state of mixture.

The transparent conductive layer can be formed by coating a basematerial with a transparent-conductive-layer-forming coating materialcontaining at least two types of metallic microparticles having anaverage grain size of 100 nm or less, then baking at a temperature of150-250° C. When the average grain size of the metallic microparticlesis 100 nm or less, then fusion and alloying of the particles is promotedeven at relatively low baking temperatures of 150-250° C., so as to forma transparent conductive film having both excellent conductivity andtransparency. In view of the fusion and alloying of the metallicmicroparticles, the average grain size of the metallic microparticlesshould particularly be 20 nm or less.

On the other hand, if the average grain size of the metallicmicroparticles in the transparent-conductive-layer-forming coatingmaterial exceeds 100 nm, then the absorption of light by the coatingfilm becomes too high to obtain a transparent conductive film having apractical level of transparency.

The above-described transparent-conductive-layer-forming coatingmaterial should preferably contain at least two types of metallicmicroparticles and contain alcohol in an amount of at least 45% byweight. The alcohol lowers the viscosity and surface tension of thecoating material containing the metallic microparticles so as to form acoating film of uniform thickness, and is particularly effective inpreventing secondary granulation of the metallic microparticles. Thiseffect is not fully activated if the content of the alcohol is less than45% by weight.

While there are no particular restrictions as to the type of alcoholwhich may be used in the transparent-conductive-layer-forming coatingmaterial, lower alcohols, higher alcohols, and glycols may be used.Particularly in view of lowering the viscosity and surface tension ofthe coating material, it is preferable to use lower alcohols having 1-4carbon atoms; for example, methyl alcohol, ethyl alcohol, n-propylalcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol,tert-butyl alcohol, or a mixture of two or more of these.

Aside from the at least two types of metallic microparticles and thealcohol, the above-described transparent-conductive-layer-formingcoating material may also contain inorganic microparticles comprisingoxides, composite oxides, or nitrides of silicon, aluminum, zirconium,cerium, titanium, yttrium, zinc, magnesium, indium, tin, antimony, orpotassium, especially oxides, composite oxides, or nitrides of indium asprincipal components, for the purposes of further increasing thetransparency of the transparent conductive film. The average grain sizeof these inorganic microparticles should preferably be 100 nm or less,and more preferably 50 nm or less, for the same reasons as mentionedabove.

The above-mentioned transparent-conductive-layer-forming coatingmaterial may also contain binder components for increasing the filmstrength of the transparent conductive film. Examples of bindercomponents which may be used include organic synthetic resins such aspolyester resins, acrylic resins, epoxy resins, melamine resins,urethane resins, butyral resins, and ultraviolet-hardening resins,hydrolysates of alkoxides of metals such as silicon, titanium, andzirconium, and organic/inorganic binder components such as siliconemonomers and silicone oligomers.

In particular, it is preferable to use as binders compounds expressed bythe following formula:

    M(OR).sub.m R.sub.n

(wherein M represents Si, Ti, or Zr, R represents a C₁ -C₄ alkyl group,m represents an integer of 1-4, n represents an integer of 0-3, and m+nequals 4), partial hydrolysates thereof, or mixtures of more typesthereof.

The binder component should preferably be added in an amount of 10% byweight or less because it can cause the conductivity of the transparentconductive film to be reduced if added in an excessive amount.

In order to increase the affinity between the binder component and themetallic microparticles, the surfaces of the metallic microparticles maybe treated with coupling agents such as silicone coupling agents andtitanate coupling agents, or with lipophilic surface-treating agentssuch as carboxylic acid salts, polycarboxylic acid salts, phosphoricester salts, sulfonic acid salts, or polysulfonic acid salts.

Furthermore, the transparent-conductive-layer-forming coating materialmay contain various types of surfactants and/or be pH-adjusted in orderto maintain the dispersion stability of the metallic microparticles inthe coating material if required. Examples of surfactants which can beused for this purpose include anionic surfactants such as polycarboxylicacid salt types, sulfonic acid salt types, and phosphoric ester types,macromolecular surfactants such as polyvinyl alcohols, polyvinylpyrrolidone, polyethylene glycol, and cellulose, and cationicsurfactants such as amine salt types. Additionally, the pH may beadjusted by adding inorganic acids, inorganic bases, or organic bases.Furthermore, aside from the above-mentioned dispersion stabilizers, itis possible to add silicone type surfactants or fluorine typesurfactants in order to adjust the leakage and sealability with respectto display screen base materials such as glass or plastics.

The method for producing the transparent-conductive-layer-formingcoating material is not particularly restricted. For example, it may beproduced by mixing a colloid solution containing at least two types ofmetallic microparticles with the above-described alcohols, inorganicmicroparticles, and binders as needed, and uniformly blending byconventionally used dispersion techniques such as by using an ultrasonicmixer or a sand mill.

As an example, the transparent conductive layer can be formed by thefollowing methods. One method involves separately preparing colloidaldispersion fluids which each contain a single type of metallicmicroparticle having an average grain size of 100 nm or less, forexample a silver sol and a palladium sol, then mixing these together ina designated proportion and adding the above-mentioned alcohols,transparent inorganic microparticles and/or binders as needed in orderto prepare a transparent-conductive-layer-forming coating materialcontaining at least two types of metallic microparticles, uniformlycoating a base material of a display screen with this coating materialsuch that the content of the metals in the transparent conductive layerafter drying will become at least 10% by weight, drying, and baking forone hour at a constant temperature in the range of 150-250° C.

Another method for forming the transparent conductive layer involvesseparately preparing colloidal dispersion fluids such as a silver soland a palladium sol which each contain a single type of metallicmicroparticle having an average grain size of 100 nm or less and theabove-mentioned alcohols, transparent inorganic microparticles and/orbinders as needed, uniformly coating a base material with these coatingmaterials in order such that the proportions of the metals in thetransparent conductive layer after drying will become a designatedvalue, drying, and baking. There are no particular restrictions for theorder of coating in this method.

The transparent conductive film of the present invention can be formedby coating a base material of a display screen or the like with theabove-described transparent-conductive-layer-forming coating material,and baking to form a film. The coating can be performed using anycommonly known thin film coating technique, such as spin coating, rollcoating, knife coating, bar coating, spray coating, meniscus coating,dip coating, or gravure printing. Of these, spin coating is anespecially preferable coating method because it enables the formation ofa thin film having a uniform thickness in a short period of time.

After coating, the coating film is dried, then baked at 150-250° C. toform a transparent conductive layer on the surface of the base material.The resulting transparent conductive layer may form a smooth coat, ormay have a lamina structure having irregularities, a mesh structure, ora plumose structure.

It was discovered that due to the extremely small particle size of themetallic microparticles in the transparent-conductive-layer-formingcoating material, when forming a coating film, at least a portion fusesto form a continuous metallic thin film even at surprisingly low bakingtemperatures of 150-250° C. at which normal coarse particles do notfuse. This is clear from observations made by microscopes. Additionally,for example, when a coating film containing palladium microparticles andsilver microparticles having an average grain size of 20 nm or less wasbaked at 175° C., the surface resistively of the thin film was as low as100-1000 Ω/square, thus indicating a reduction in the intergranularresistance. Since this effect is particularly evident when silverparticles which have a relatively low melting point are present, thesurface resistivity of the thin film can be greatly improved incomparison to the case of using only palladium microparticles even ifthe amount of silver particles is on the order of only a few % byweight.

Additionally, it was discovered that an alloy is produced in a metallicthin film wherein at least two types of metallic microparticles arefused. This is clear from X-ray diffraction of a sample formed by bakinga coating film containing palladium microparticles and silvermicroparticles at 175° C., in which peaks due to the presence ofpalladium and silver cannot be recognized while a single peak due to aPd--Ag alloy can be observed, as shown in FIG. 2. Due to the productionof this alloy, the transparent conductive film of the present inventionhas high conductivity, while also gaining a high level of durabilitywith respect to saline resistance, acid resistance, oxidationresistance, and ultraviolet resistance.

The thickness of the transparent conductive layer should preferably bewithin the range of 5-200 nm. In particular, good transparency can beobtained while retaining sufficient static prevention effects andelectromagnetic shielding effects by making the thickness within therange of 5-50 nm. At a thickness of less than 5 nm, not only does itbecome difficult to obtain sufficient electromagnetic shielding effects,but it also becomes difficult to form a uniform film. On the other hand,if the thickness exceeds 200 nm there are no problems in theconductivity, but the transparency is reduced, thereby reducing thevisibility of the transmitted images.

The total content of the at least two types of metals in the transparentconductive film should be selected so as to enable the desiredelectromagnetic shielding effects to be obtained in consideration of theabove-mentioned film thickness.

In general, electromagnetic shielding effects can be expressed by thefollowing Equation 1: ##EQU1## (wherein S(dB) represents theelectromagnetic shielding effect, ρ (Ω·cm) represents the volumeresistivity of the conductive film, f (MHz) represents theelectromagnetic frequency, and t (cm) represents the thickness of theconductive film).

In this case, the thickness t is extremely thin as mentioned above, sothat the electromagnetic shielding effect S can be approximated by thefollowing Equation 2 by ignoring the term with the thickness t inEquation 1. ##EQU2##

That is, a greater shielding effect will be generated with respect to awide range of frequencies of electromagnetic waves if the volumeresistivity (ρ) of the transparent conductive film is made as small aspossible. Generally, electromagnetic shielding effects are considered tobe effective if S>30 dB and exceptional if S>60 dB. Since the frequencyof the electromagnetic waves which are to be controlled is generally inthe range of 10 kHz-1000 MHz, the volume resistivity (ρ) of thetransparent conductive layer should preferably be less than or equal to10³ Ω·cm in order to obtain good electromagnetic shielding effects witha film thickness of 200 nm or less.

In order to fulfill this condition, the transparent conductive layershould contain metal in an amount of at least 10% by weight. If themetallic content is less than 10% by weight, the conductivity will bereduced so as to make it difficult to obtain substantial electromagneticshielding effects.

If the transparent conductive layer is colored due to the content ofmetals other than palladium, the hue can also be adjusted by suppressingthe light absorption characteristics of the metal in the transparentconductive film by means of ultraviolet irradiation, infraredirradiation, microwave irradiation, X-ray irradiation, or gamma rayirradiation.

The transparent conductive film of the present invention may also beformed from a single transparent conductive layer or may be formed froma lamination of a plurality of transparent conductive layers oftransparent thin films which do not have electrical conductioncapabilities.

Next, the low-reflectivity transparent conductive film of the presentinvention shall be explained.

This low-reflectivity transparent conductive film has at least one layerof a transparent thin film having a refractive index different from therefractive index of the transparent conductive layer above or below thetransparent conductive film. This transparent thin film eliminates andreduces the reflection of ambient light from the boundaries of the filmby means of an interference effect, and is used to confer ananti-reflective effect to the transparent conductive film. Thistransparent thin film is not necessarily restricted to a single layer,and may be formed from multiple layers.

Generally, boundary reflection prevention capabilities in multi-layeredthin films are determined by the refractive indices and thicknesses ofthe thin films and the number of laminated thin films. Consequently,effective anti-reflection effects can be conferred to thelow-reflectivity transparent conductive film of the present invention aswell by appropriately designing the transparent conductive film and thetransparent thin films by considering the number of laminated films.

The transparent thin films not only prevent reflection at the boundariesin a multi-layered thin film but also can be expected to have an effectof protecting the screen from external forces when used on a displayscreen of a display device. Therefore, it is preferable for atransparent thin film having sufficient strength for practical purposesand having a lower refractive index than the transparent conductive filmto be provided above the transparent conductive film. As a result, it ispossible to obtain a low-reflectivity transparent conductive film whichis practical for use in display devices such as cathode ray tubes andplasma displays.

Examples of materials capable of forming the transparent thin filminclude thermoplastic, heat-hardening, and light/electron beam hardeningresins such as polyester resins, acrylic resins, epoxy resins, andbutyral resins; hydrolysates of alkoxides of metals such as silicon,aluminum, titanium, and zirconium; and silicone monomers and siliconeoligomers, which may be used either alone or as mixtures.

A particularly favorable transparent thin film is an of SiO₂ thin filmwhich has a high surface hardness and a relatively low refractive index.An example of a material capable of forming such an SiO₂ thin film is acompound as expressed by the following formula:

    Si(OR).sub.m R.sub.n

(wherein R represent a C₁ -C₄ alkyl group, m represents an integer of1-4, n represent an integer of 0-3, and m+n equals 4), partialhydrolysates thereof, or mixtures of one or more types thereof. As anexample of such a compound, tetraethoxysilane (Si(OC₂ H₅)₄) which issuitable for use in view of the ability to form a thin film, thetransparency, film strength, and anti-reflective capabilities.

If they allow the transparent thin film to be adjusted to a differentrefractive index from the transparent conductive film, it is alsopossible to add various types of resins, metal oxides, composite oxides,or nitrides, or precursors which generate these due to baking.

The formation of the transparent thin film can be performed by anymethod wherein a coating fluid (transparent-thin-film-forming coatingmaterial) containing the above-mentioned components is uniformly coated,as with the method of forming the transparent conductive film. While thecoating can be performed by spin coating, roll coating, knife coating,bar coating, spray coating, meniscus coating, dip coating, gravureprinting, or the like, spin coating is particularly preferable. Aftercoating, the coating film is dried, and a hard film is formed,preferably by means of baking or light/electron beam irradiation.

The low-reflectivity transparent conductive film of the presentinvention may have a transparent rough layer, i.e. a transparent filmhaving a roughened profile, as the outermost layer. This transparentrough layer has the effect of scattering light reflected form thesurface of the low-reflectivity transparent conductive film so as toconfer an anti-glare effect to the display screen. In order to obtain asufficient anti-glare effect, it is preferable to form a roughenedsurface such that the gloss value (shininess) is reduced by 10-40%,preferably 20-40%, from the gloss value with a flat surface. If thereduction in the gloss value exceeds 40%, this is often accompanied withthe haze value exceeding 3%, in which case the film surface can becomewhitened so as to reduce the visibility such as the image resolution ofthe transmitted images.

The shape of the rough surface of the transparent rough layer can beappropriately selected depending on the purpose, such as to reduce thereflection of ambient light and to enable the transmitted image to beclearly perceptible. Examples of typical shapes include shapes whereinmultiple hemispherical or conical bumps or notches are regularly orirregularly distributed on the surface, shapes wherein multiplerib-shaped projections and depressions are arranged in a blind-fashionor in waves, and shapes wherein multiple regular or irregular groovesare formed on a flat surface.

With any of the above shapes, the height difference of theirregularities (the difference in height between the tops of theprojections and the bottoms of the depressions) should preferably bewithin the range of 0.01-1 μm on average in order to obtain a reductionof the gloss value in the range of 20-40%. When the height difference isless than 0.01 μm, the resulting surface is a substantially flatsurface, and it is not possible to obtain sufficient anti-glare effects.On the other hand, if the height difference exceeds 1 μm, the hazeincreases so as to reduce the resolution of the transmitted images.

In order to form a transparent rough layer on the upper surface of thetransparent conductive film, it is possible to use a method of forming adiscrete layer (microparticle layer) by spraying a transparent coatingmaterial with an appropriately adjusted viscosity onto the transparentthin film, then baking. Additionally, it can also be formed by coatingthe transparent thin film with a uniform thickness of a transparentcoating material containing transparent microparticles such as SiO₂microparticles and a medium, then evaporating the solvent so as to formirregularities with the transparent microparticles. Furthermore, it isalso possible to form irregularities on a flat transparent conductivefilm surface by means of embossing or etching.

If the refractive index of the transparent rough layer is set to arefractive index different from that of the transparent conductivelayer, then the transparent rough layer will be effective not only inscattering ambient light reflections but also in preventing interlayerreflections. Additionally, the transparent rough layer should preferablybe made into a hard coat as with the transparent thin film in view ofthe film strength and the anti-reflective capabilities. When consideringthese points, the transparent rough layer should preferably be formedusing a coating material identical to that used to form a transparentthin film, such as a tetraethoxysilane coating material, for thepurposes of film strength and anti-reflective effects.

At least one layer constituting the low-reflectivity transparentconductive film of the present invention may contain a colorant. Thiscolorant is added for adjusting the hue of the transmitted images bymasking so as to provide a natural appearance and for improving thechromatic contrast of the transmitted images, when there are deviationsin the spectrum of transmitted light due to the metals contained in thetransparent conductive layer. For example, when silver is used as onetype of metal, the transparent conductive layer will be given ayellowish color because silver absorbs light in the lower wavelengths of400-530 nm in the visible range, thus making the hue of the transmittedimages appear unnatural. The addition of a colorant has the effect ofcorrecting this to flatten the spectrum of the transmitted light overthe entire visible wavelength range, thereby improving the hue of thetransmitted images.

Colorants which are appropriate for use in the low-reflectivitytransparent conductive film of the present invention are blue, violet,and black colorants. Among these, violet pigments and blue pigments areespecially effecting in toning transmitted images, and while blackpigments also have a toning effect, they additionally have the effect ofincreasing the chromatic contrast of the transmitted images.

Examples of colorants which are suitable for use include organic andinorganic pigments such as phthalocyanine blue, cyanine blue,indanthrone blue, dioxazine violet, aniline black, alkali blue, titaniumoxide, chrome oxide, iron black, cobalt blue, cerulean blue, zincchromate, ultramarine blue, manganese violet, cobalt violet, prussianblue, and carbon black; and blue, violet, or black dyes such as azodyes, anthraquinone dyes, indigoid dyes, phthalocyanine dyes, carboniumdyes, quinoneimine dyes, methine dyes, quinoline dyes, nitro dyes,nitroso dyes, benzoquinone dyes, naphthoquinone dyes, naphthalimidedyes, and perinone dyes.

However, the low-reflectivity transparent conductive film of the presentinvention may also contain colorants for hues other than for toningpurposes, such as for giving the screen a specific color.

Additionally, aside from the conventional colorants mentioned above, itis possible to use other colorants which have been used for proposed fortransparent conductive films or the display screens of cathode raytubes, for example, those which have filter effects of selectivelyabsorbing visible light other than the three primary colors (forexample, see Japanese Patent Application, First Publication No. Hei1-320742, Japanese Patent Application, First Publication No. Hei3-11532, and Japanese Patent Application, First Publication No. Hei3-254048), those which obtain high-contrast effects by reducing overalltransmissivity of visible light (for example, see Japanese PatentApplication, First Publication No. Hei 6-80903), those which obtainanti-reflective effects by using colorants which roughly correspond tothe minimum reflectivity in an anti-reflective film due to absorption oflight in a lamination (for example, see Japanese Patent Application,First Publication No. Hei 5-203804), and those which obtain naturalimages which are soft on the eyes by absorbing visible light of specificwavelengths (for example, Japanese Patent Application, First PublicationNo. Hei 7-151903).

The low-reflectivity transparent conductive film of the presentinvention can be applied effectively to the display screens of varioustypes of display devices such as cathode ray tubes, plasma displays,liquid crystal displays, touch panels, and electro-optic displaydevices, the windows of automobiles and buildings, and the view windowsof microwave ovens.

The display device of the present invention has the above-mentionedlow-reflectivity transparent conductive film formed on the displayscreen. This display device prevents the accumulation of staticelectricity on the display screen so that dust does not adhere to theimage display screen, shields electromagnetic waves so that varioustypes of electromagnetic disturbances are prevented, has exceptionallight transmission so that the images are bright, has a uniformthickness so that the outer appearance of the display screen isimproved, has controlled reflection so that the visibility is good, andhas high durability with respect to saline resistance, acid resistance,oxidation resistance, and ultraviolet resistance so that conductivity isnot lost even in metal-corrosive environments such as in saline water orsunlight.

In particular, the display device of the present invention wherein thetransparent conductive film contains palladium is highly resistant tothe halogen salts contained in salt components due to seawater and thesweat of operators during transport, hydrogen sulfide gases in hotspring areas, acidic liquids such as SO_(x) gases and acid rain in theatmosphere, and oxide gases such as ozone which are generated byultraviolet radiation, and is capable of maintaining the initialperformance such as with respect to anti-static effects, electromagneticshielding effects, anti-reflective effects, hue, and film strength overlong periods of time, even when placed under environmental conditionswhich include such degrading factors.

EXAMPLES

Hereinbelow, the present invention shall be explained in detail by meansof examples, but the present invention is not restricted by theseexamples in any way.

The following were prepared as base fluids common to both the examplesand the comparative examples.

(Aqueous Palladium Sol)

An aqueous solution containing 0.15 mmol/l of palladium chloride and anaqueous solution containing 0.024 mmol/l of sodium boron hydride weremixed together, and the resulting colloidial dispersion fluid wasconcentrated to obtain an aqueous sol containing 0.189 mol/l ofpalladium microparticles (average grain size 10 nm).

(Aqueous Platinum Sol)

An aqueous solution containing 0.25 mmol/l of chloroplatinic acidhydrate and an aqueous solution containing 0.15 mmol/l of sodium boronhydride were mixed together, and the resulting colloidal dispersionfluid was concentrated to obtain an aqueous sol containing 0.103 mol/lof platinum microparticles (average grain size 10 nm).

(Aqueous Silver Sol)

While holding an aqueous solution (60 g) having sodium citrate dihydrate(14 g) and ferrous sulfate (7.5 g) dissolved therein at 5° C., anaqueous solution (25 g) having silver nitrate (2.5 g) dissolved thereinwas added to obtain a silver sol having a reddish brown color. Afterremoving impurities from this silver sol by centrifugal separation andrinsing, purified water was added to obtain an aqueous sol containing0.185 mol/l of silver microparticles (average grain size 10 nm).

(Transparent-Thin-Film-Forming Coating Material)

Tetraethoxysilane (0.8 g), 0.1 N hydrochloric acid (0.8 g) and ethylalcohol (98.4 g) were mixed together to form a uniform aqueous solution.

Example 1 Preparation of Transparent-Conductive-Film-Forming CoatingMaterial

    ______________________________________                                        Aqueous Palladium Sol                                                                            15 g                                                       Aqueous Silver Sol 35 g                                                       Isopropyl Alcohol  10 g                                                       Ethyl Alcohol      40 g                                                       ______________________________________                                    

The above-listed components were mixed together, then the resultingfluid mixture was made into a dispersion by an ultrasonic dispersingmachine (BRANSON ULTRASONICS "Sonifier 450"), to prepare thetransparent-conductive-film-forming coating material of Example 1.

Film Formation:

The above-described transparent-conductive-film-forming coating materialwas coated onto the display screen of a Braun tube using a spin coater.After drying, the above-described transparent-thin-film-forming coatingmaterial was coated onto the coating surface in the same manner using aspin coater, then this Braun tube was put into a dryer and baked for onehour at 150° C. to form a low-reflectivity transparent conductive film,thereby producing a cathode ray tube having a reflection preventing,high-conductivity film according to Example 1.

Example 2 Preparation of Transparent-Conductive-Film-Forming CoatingMaterial

    ______________________________________                                        Aqueous Palladium Sol                                                                            35 g                                                       Aqueous Silver Sol 15 g                                                       Isopropyl Alcohol  10 g                                                       Ethyl Alcohol      40 g                                                       ______________________________________                                    

The above-listed components were mixed together, then processed in thesame manner as with Example 1 to prepare thetransparent-conductive-film-forming coating material of Example 2.

Film Formation:

The above-described transparent-conductive-film-forming coating materialwas used and treated in the same manner as with Example 1 to produce acathode ray tube having a reflection preventing, high-conductivity filmaccording to Example 2.

Example 3 Preparation of Transparent-Conductive-Film-Forming CoatingMaterial

    ______________________________________                                        Aqueous Palladium Sol                                                                            45 g                                                       Aqueous Silver Sol  5 g                                                       Isopropyl Alcohol  10 g                                                       Ethyl Alcohol      40 g                                                       ______________________________________                                    

The above-listed components were mixed together, then processed in thesame manner as with Example 1 to prepare thetransparent-conductive-film-forming coating material of Example 3.

Film Formation:

The above-described transparent-conductive-film-forming coating materialwas used and treated in the same manner as with Example 1 to produce acathode ray tube having a reflection preventing, high-conductivity filmaccording to Example 3.

Example 4 Preparation of Transparent-Conductive-Film-Forming CoatingMaterial

    ______________________________________                                        Aqueous Palladium Sol                                                                            25 g                                                       Aqueous Silver Sol 25 g                                                       Isopropyl Alcohol  10 g                                                       Ethyl Alcohol      40 g                                                       ______________________________________                                    

The above-listed components were mixed together, then processed in thesame manner as with Example 1 to prepare thetransparent-conductive-film-forming coating material of Example 4.

Film Formation:

The above-described transparent-conductive-film-forming coating materialwas used and treated in the same manner as with Example 1 to produce acathode ray tube having a reflection preventing, high-conductivity filmaccording to Example 4.

Example 5 Preparation of Transparent-Conductive-Film-Forming CoatingMaterial

    ______________________________________                                        Aqueous Palladium Sol                                                                           12.5        g                                               Aqueous Platinum Sol                                                                            12.5        g                                               Aqueous Silver Sol                                                                              25          g                                               Isopropyl Alcohol 10          g                                               Ethyl Alcohol     40          g                                               ______________________________________                                    

The above-listed components were mixed together, then processed in thesame manner as with Example 1 to prepare thetransparent-conductive-film-forming coating material of Example 5.

Film Formation:

The above-described transparent-conductive-film-forming coating materialwas used and treated in the same manner as with Example 1 to produce acathode ray tube having a reflection preventing, high-conductivity filmaccording to Example 5.

Comparative Example 1 Preparation of Transparent-Conductive-Film-FormingCoating Material

    ______________________________________                                        Aqueous Silver Sol                                                                             50 g                                                         Isopropyl Alcohol                                                                              10 g                                                         Ethyl Alcohol    40 g                                                         ______________________________________                                    

The above-listed components were mixed together, then processed in thesame manner as with Example 1 to prepare thetransparent-conductive-film-forming coating material of ComparativeExample 1.

Film Formation:

The above-described transparent-conductive-film-forming coating materialwas used and treated in the same manner as with Example 1 to produce acathode ray tube having a reflection preventing, high-conductivity filmaccording to Comparative Example 1.

Comparative Example 2 Preparation of Transparent-Conductive-Film-FormingCoating Material

    ______________________________________                                        Antimony-doped Tin Oxide Powder (SUMITOMO OSAKA                                                            1.5 g                                            CEMENT, average grain size 0.01 μm)                                        Purified Water              78.5 g                                            Butyl Cellosolve            10.0 g                                            IPA                         10.0 g                                            ______________________________________                                    

The above-listed components were mixed together, then made into adispersion by an ultrasonic dispersing machine (BRANSON ULTRASONICS"Sonifier 450"), to prepare the transparent-conductive-film-formingcoating material of Comparative Example 2.

Film Formation:

The above-described transparent-conductive-film-forming coating materialwas coated onto the display screen of a Braun tube using a spin coater.After drying, the above-described transparent-thin-film-forming coatingmaterial was coated onto the coating surface in the same manner using aspin coater, then a low-reflectivity transparent conductive film wasformed by baking in a dryer for one hour at 150° C., thereby producing acathode ray tube having a reflection preventing, high-conductivity filmaccording to Comparative Example 2.

The type and quantities of metals contained in thetransparent-conductive-film-forming coating materials according to theabove-described Examples 1-5 and Comparative Examples 1 and 2 are shownin Table 1.

                  TABLE 1                                                         ______________________________________                                                                    Metal Content                                     Coating Material                                                                              Types of Metals                                                                           (parts by wt.)                                    ______________________________________                                        Example 1       Pd          0.3                                                               Ag          0.7                                               Example 2       Pd          0.7                                                               Ag          0.3                                               Example 3       Pd          0.9                                                               Ag          0.1                                               Example 4       Pd          0.5                                                               Ag          0.5                                               Example 5       Pd          0.25                                                              Pt          0.25                                                              Ag          0.50                                              Comparative Example 1                                                                         Ag          1.0                                               Comparative Example 2                                                                         ATO*.sup.1) 1.0                                               ______________________________________                                         *.sup.1) antimonydoped tin oxide                                         

(Evaluatory Measurements)

The properties of the low-reflectivity transparent conductive filmsformed on the cathode ray tubes were measured by means of the followingdevices or methods.

Transmissivity: TOKYO DENSHOKU "Automatic Haze Meter H III DP"

Haze: TOKYO DENSHOKU "Automatic Haze Meter H III DP"

Surface Resistance: MITSUBISHI CHEMICAL CORP. "Rolesta AP" (4-terminalmethod)

Transmissivity Difference: HITACHI, LTD. "U-3500" automatic-recordingspectrophotometer was used to determine the difference between themaximum transmissivity and minimum transmissivity in the visible lightrange. (The smaller the maximum-minimum transmissivity difference in thevisible light range, the flatter the transmissivity, and the clearer thehue of the transmitted images. Particularly when 10% or less, the colorof the transmitted images approaches black, and a high degree of clarityis obtained.)

Reflectivity: EG&G GAMMASCIENTIFIC "Model C-11"

Electromagnetic Shielding: Calculated by the above-given Equation 1 at astandard of 0.5 MHz.

Saline Resistance: Electromagnetic shielding at 0.5 MHz after 3 days ofimmersion in saline.

Interplaner Spacing: The interplaner spacing of the conductive materialwas measured using an X-ray diffraction device. The X-ray diffractionvalues indicate the interplaner spacings of the (1,1,1) plane inExamples 1-5 and Comparative Example 1, and of the (1,1,0) plane inComparative Example 2, with the values in the () indicating thetheoretical values.

The measurement results are shown in Tables 2 and 3.

                  TABLE 2                                                         ______________________________________                                                                Surface                                                      Transmissivity                                                                         Haze    Resistance                                                                             Transmissivity                                      (%)      (%)     (Ω/square)                                                                       Difference (%)                               ______________________________________                                        Example 1                                                                              70.1       0.0     1 × 10.sup.2                                                                   10                                         Example 2                                                                              70.1       0.0     5 × 10.sup.2                                                                   3                                          Example 3                                                                              70.3       0.0     8 × 10.sup.2                                                                   2                                          Example 4                                                                              70.5       0.0     3 × 10.sup.2                                                                   5                                          Example 5                                                                              71.2       0.0     5 × 10.sup.2                                                                   8                                          Comparative                                                                            76.3       0.1     6 × 10.sup.2                                                                   20                                         Example 1                                                                     Comparative                                                                            102.7      0.1     5 × 10.sup.7                                                                   1                                          Example 2                                                                     ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                                      0.5 MHz Electro-                                                Reflectivity  Magnetic    Saline   Interplaner                                (%)           Shielding (dB)                                                                            Resistance                                                                             Spacing (Å)                            ______________________________________                                        Example 1                                                                             0.6       87.2        82.5   2.33 (2.33)                              Example 2                                                                             0.3       80.2        80.1   2.27 (2.28)                              Example 3                                                                             0.5       78.2        78.2   2.25 (2.26)                              Example 4                                                                             0.2       82.4        81.8   2.30 (2.30)                              Example 5                                                                             0.4       80.2        79.4   2.31 (2.31)                              Comparative                                                                           0.9       75.0        10.1   2.36 (2.36)                              Example 1                                                                     Comparative                                                                           1.0       56.0        56.0   3.36 (3.35)                              Example 2                                                                     ______________________________________                                    

The results of Tables 2 and 3 show that the cathode ray tube samples ofExamples 1-5 which have low-reflectivity transparent conductive filmshaving transparent conductive layers containing at least two types ofmetals in a total of at least 10% by weight on the display screens allhave favorable transmissivities, small transmissivity differences, lowreflectivity, and no substantially detectable haze, so that thetransmitted images are bright, have a natural hue, and are sharp.Additionally, the surface resistance is small, so that the anti-staticeffect is large, and the electromagnetic shielding effects areexcellent. Furthermore, the fact that they have exceptional salineresistance indicates that they also have exceptional durability.

The measurement results for the interplaner spacing of the X-rayanalysis indicate that the metals in the transparent conductive layersof Examples 1-5 were detected as single-substance peaks, which roughlymatched the interplaner spacings (theoretical values) of alloys composedfrom ratios of Pd:Ag=3:7, Pd:Ag=7:3, Pd:Ag=9:1, Pd:Ag=5:5, andPd:Pt:Ag=2.5:2.5:5.0, thus demonstrating that these two or three typesof metals formed alloys in the transparent conductive layers.

In contrast thereto, the cathode ray tube of Comparative Example 1having a conventionally known low-reflectivity transparent conductivefilm has a transparent conductive layer composed of microparticles of asingle metal (Ag) and therefore has a high transmissivity difference inthe spectrum transmitted visible light, so that there was a deviation inthe hue, and the colors of the transmitted images appeared unnatural.Additionally, the reflection was high, and haze was observed, so thatthe perceptibility was deficient. Furthermore, the saline resistance wasextremely low, so that the durability was deficient. On the other hand,the cathode ray tube of Comparative Example 2 had a transparentconductive layer composed of antimony-doped tin oxide, having a highreflectivity and exhibiting haze, so that the perceptibility wasdeficient. Additionally, the surface resistance was high so that theelectromagnetic shielding was deficient, so that the value essentiallyas a low-reflectivity electromagnetic shielding display device was lowin comparison to the cathode ray tube of the present invention.

INDUSTRIAL APPLICABILITY

As described above, the transparent conductive film of the presentinvention has a transparent conductive layer containing at least twotypes of metals in a total amount of at least 10% by weight, as a resultof which the transparency, tonability and conductivity are high, thestatic prevention effects and electromagnetic shielding effects areexceptional, and the tone of the transmitted images is controlled.Furthermore, the durability is exceptional with respect to salineresistance, acid resistance, oxidation resistance, ultravioletresistance, and the like, and the transparent conductive film can beused advantageously for the static prevention and electromagneticshielding of various types of display devices.

Since the low-reflectivity transparent conductive film of the presentinvention has the above-mentioned transparent conductive layer as anupper layer and/or a bottom layer, and has at least one layer of atransparent thin film having a refractive index different from therefractive index of the transparent conductive layer, anti-reflectioncapabilities are conferred in addition to the above-mentionedproperties, the static prevention effects and electromagnetic shieldingeffects are exceptional, the tone of transmitted images is controlled,and the durability is exceptional with respect to saline resistance,acid resistance, oxidation resistance, and ultraviolet resistance, andambient light reflection and haze are also suppressed so as to result intransmitted images which are clear and have good perceptibility.

The display device of the present invention has the above-mentionedlow-reflectivity transparent conductive film formed on the displayscreen, so that dust will not adhere to the image screen,electromagnetic waves are effectively shielded so as to prevent variouselectromagnetic disturbances, the light transmission is exceptional sothat images are bright, the film thickness is uniform so that theappearance of the display screen is improved, the reflection issuppressed so that the perceptibility is good, and the durability ishigh such as with respect to saline resistance, acid resistance,oxidation resistance, and ultraviolet resistance so that theconductivity is not lost even in metal-corrosive environments such as insaline and sunlight.

Accordingly, the transparent conductive film and low-reflectivitytransparent conductive film of the present invention can be effectivelyapplied to various types of display devices such as cathode ray tubes oftelevisions and computer displays, plasma displays, liquid crystaldisplay devices, touch panels, and electro-optic display devices, thetransparent electrodes of solar batteries, the transparent conductiveportions of transparent heating elements, or devices which radiateelectromagnetic waves, or can be adhered to glass, building materials,or the like, such as for the windows of surgery rooms, broadcastingstudios, OA installations, and automobiles/buildings, or to the viewwindows of microwave ovens.

Additionally, the display device of the present invention has highdurability even under severe conditions, and is capable of maintainingreflection prevention, static prevention, and electromagnetic shieldingeffects over long periods of time.

What is claimed is:
 1. A display device comprising transparentconductive film formed on a display screen, the transparent conductivefilm having a transparent conductive layer containing metals in anamount of at least 10% by weight, at least two types of the metals beingpalladium and silver, the weight ratio of palladium:silver being withinthe range of 30:70 to 99:1.
 2. A display device in accordance with claim1, wherein at least a portion of the metals in said transparentconductive layer are fused to form a continuous metallic thin film.
 3. Adisplay device in accordance with claim 1, wherein at least a portion ofthe at least two types of metals in said transparent conductive layerform an alloy.
 4. A display device in accordance with claim 1, whereinat least one transparent thin film is provided above and/or below saidtransparent conductive film, having a refractive index different fromthe refractive index of said transparent conductive layer.
 5. A displaydevice in accordance with claim 4, wherein said transparent thin filmcontains SiO₂.
 6. A display device in accordance with claim 4, wherein atransparent rough layer is formed as an outermost layer of saidlow-reflectivity transparent conductive film.
 7. A display device inaccordance with claim 4, wherein at least one layer constituting saidlow-reflectivity transparent conductive film contains a colorant.
 8. Atransparent-conductive-film-forming coating material comprising silverparticles having an average grain size of 100 nm or less, palladiumparticles having an average grain size of 100 nm or less, and alcohol inan amount of at least 45% by weight, the weight ratio ofpalladium:silver being within the range of 30:70 to 99:1.
 9. A processfor producing a display device, the process comprising applying thetransparent-conductive-film-forming coating material according to claim8 on a display screen and then baking the display screen at atemperature within the range of 150-250° C.